1. Field of the Invention
This invention relates to a method for connecting a pipe fitting to a pipe. In one aspect, this invention relates to a method for connecting a pipe fitting to a wall of a pipe, which pipe is underground and in-service. In one aspect, this invention relates to a method for connecting a plastic pipe fitting with a plastic pipe using fusion means for fusing the plastic pipe fitting with the plastic pipe. In another aspect, this invention relates to a method for connecting a pipe fitting to a wall of an underground pipe without substantial excavation to expose the pipe.
2. Description of Related Art
Access to underground natural gas pipelines to perform tasks such as internal pipe inspection, pipe repair, and the connection of pipe fittings to the pipe to enable a variety of activities requiring access to the interior of the pipe, such as the connection of natural gas service lines between the customers and the underground pipeline supply, generally requires excavation to expose the underground pipeline. The standard technique for accessing the underground pipes involves excavation through three-feet-by-four-feet bell holes followed by appropriate restoration, which frequently requires the use of heavy equipment, e.g. backhoes and dump trucks, to remove the ground covering the pipeline and restore the ground after completion of work on the pipeline.
In recent years, keyhole technology has been used by some utilities and contractors to perform the required excavation. Keyhole technology is the practice of carrying out repairs, maintenance, and other procedures on underground utility piping from above ground with the assistance of long-handled tools and typically requires an opening in the ground no larger than about 18 inches across. The limited amount of available space in which to work on the exposed pipeline has required the development of a variety of new tools and procedures for performing the required tasks on the pipeline. One of the tasks frequently performed is the connection of a pipe fitting. Current state-of-the-art involves connection of the pipe fitting by a variety of means to the external surface of the pipe wall, some of which require a full encirclement of the pipeline. The pipe fittings may be connected by any of a number of available processes including electro-fusion, heat-fusion, cold adhesive fusion, and mechanical means. Electro-fusion is a process for joining two plastic components to each other in which one component comprising an embedded heating element is brought into contact with the other component and an electric power source supplies an electric current to the heating element, causing the heating element to produce heat, thereby melting the plastic material in both plastic components in the vicinity of the heating element. The melted materials of the components flow together and form a homogeneous connection following a cooling down period. Heat-fusion is a process for joining two plastic components to each other in which the components are heated to the melting temperature of the components, brought into contact with each other, and allowed to cool. Cold adhesive fusion is a process in which the two plastic components are joined together by an adhesive without heating the components.